Ihave a density of 1.61g/cm^3 and a mass of 28g. find the missing value

The missing value is the 'k' that should appear between '28' and 'g' .

Nobody has a mass of 28g.

My new grandson, who was born yesterday (January 29, 2019), had a mass of 4,039g at birth.  

Mother and son are happy and resting comfortably today, in Kfar Tapuach, Samaria, Israel.

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.